One type of prior nonvolatile memory is the flash erasable and electrically programmable read-only memory ("flash EPROM"). The flash EPROM can be programmed by a user. Once programmed, the entire contents of the flash EPROM can be erased by electrical erasure. The flash EPROM may then be reprogrammed with new data.
Like the prior art personal computer systems, one type of prior flash EPROM is typically designed to be used in the 3 volt power supply environment ("3 volt flash EPROM"). Another type of prior flash EPROM is typically designed to be used in the 5 volt power supply environment ("5 volt flash EPROM"). The 3 volt flash EPROM is typically used in the 3 volt power supply prior art personal computers and the 5 volt flash EPROM is typically used in the 5 volt power supply prior art personal computers. Many prior art desk-top computers typically employ a 5 volt power supply and many prior art laptop computers typically employ a 3 volt power supply.
One disadvantage associated with such prior flash EPROMs is that a 5 volt flash EPROM is typically unsuitable for use in a 3 volt power supply personal computer and a 3 volt flash EPROM is typically unsuitable for use in a 5 volt power supply personal computer. Mismatching the power supply of a flash EPROM with that of a personal computer typically causes the flash EPROM to operate incorrectly and, in the worst case, can cause damage to data stored in the flash EPROM. Therefore, before installing a prior flash EPROM into a personal computer, the user typically needs to know the voltage of the power supply of the personal computer and the voltage required by the flash EPROM.
Another disadvantage associated with the prior flash EPROMs is that the prior flash EPROMs typically cannot be switched between different power supply systems. Typically, when a 5 volt flash EPROM is removed from a 5 volt power supply system and placed in a 3 volt power supply system, the 5 volt flash EPROM typically cannot function properly and the data stored in that flash EPROM may be lost. Likewise, when a 3 volt flash EPROM is removed from a 3 volt power supply system and placed in a 5 volt power supply system, the 3 volt flash EPROM typically cannot function properly and the data stored may be lost. Moreover, the circuitry of flash EPROM may be damaged.